In lithography techniques, for example, a resist film composed of a resist material is formed on a substrate, and the resist film is subjected to selective exposure of radial rays such as light or electron beam through a mask having a predetermined pattern, followed by development, thereby forming a resist pattern having a predetermined shape on the resist film. A resist material in which the exposed portions become soluble in a developing solution is called a positive-type, and a resist material in which the exposed portions become insoluble in a developing solution is called a negative-type.
In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have lead to rapid progress in the field of pattern miniaturization.
Typically, these miniaturization techniques involve shortening the wavelength of the exposure light source. Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used, but nowadays KrF excimer lasers and ArF excimer lasers are starting to be introduced in mass production. Furthermore, research is also being conducted into lithography techniques that use an exposure light source having a wavelength shorter than these excimer lasers, such as F2 excimer lasers, electron beam, extreme ultraviolet radiation (EUV), and X ray.
Resist materials for use with these types of exposure light sources require lithography properties such as a high resolution capable of reproducing patterns of minute dimensions, and a high level of sensitivity to these types of exposure light sources. As a resist material which satisfies these conditions, a chemically amplified resist is used, which includes a base resin that exhibits a changed solubility in an alkali developing solution under action of acid and an acid generator that generates acid upon exposure.
Conventionally, negative resist materials for use in processes that use either i-line radiation or a KrF excimer laser (248 nm) as the light source have employed chemically amplified negative resist compositions containing a combination of an acid generator, an alkali-soluble resin such as a novolak resin or a polyhydroxystyrene, and an amino resin such as a melamine resin or urea resin (for example, see patent document 1).
Furthermore, negative resist materials that can be applied to processes that use an ArF excimer laser of even shorter wavelength use materials that exhibit improved transparency to ArF excimer lasers. For example, a negative resist composition that includes a resin component containing carboxyl groups, a cross-linker containing alcoholic hydroxyl groups, and an acid generator has been proposed.
In this composition, the carboxyl groups within the resin component react with the alcoholic hydroxyl groups of the cross-linker under the action of the acid generated from the acid generator. As a result, the resin component changes from an alkali-soluble state to an alkali-insoluble state.
Furthermore, compositions have also been proposed that include a resin component containing carboxyl groups or carboxylate ester groups as well as alcoholic hydroxyl groups, and an acid generator, wherein an intermolecular reaction between the carboxyl groups or carboxylate ester groups and the alcoholic hydroxyl groups within the resin component, under the action of the acid generated from the acid generator, causes the resin component to change from an alkali-soluble state to an alkali-insoluble state (for example, see non-patent documents 1 to 4 and patent document 2).    [Patent Document 1] Japanese Examined Patent Application, Second Publication No. Hei 08-3635    [Patent Document 2] Japanese Unexamined Patent Application, First Publication No. 2000-206694    [Non-Patent Document 1] J. Photopolym. Sci. Tech., Vol. 10, No. 4, pages 579 to 584 (1997)    [Non-Patent Document 2] J. Photopolym. Sci. Tech., Vol. 11, No. 3, pages 507 to 512 (1998)    [Non-Patent Document 3] SPIE Advances in Resist Technology and Processing XIV, Vol. 3333, pages 417 to 424 (1998)    [Non-Patent Document 4] SPIE Advances in Resist Technology and Processing XIX, Vol. 4690, pages 94 to 100 (2002)